An Israeli soldier walks by an 'Iron Dome' short-range missile defense system positioned near the northern city of Haifa on Jan. 31, 2013 in Israel. The Iron Dome missile defense system is designed to intercept and destroy incoming short-range rockets and artillery shells.

Israeli warplanes struck several targets inside Syria overnight Tuesday, including a biological weapons research center that was reportedly flattened out of concern that it might fall into the hands of Islamist extremists fighting to topple the government of Syrian president Bashar Assad, Western intelligence officials tell TIME.

So far only two airstrikes have been publicly reported, amid a flurry of conflicting initial reports. Syria officially complained of the destruction of the Scientific Studies and Research Center in Jamarya northwest of Damascus. And a variety of news organizations reported that Israeli jets hit a convoy carrying advanced anti-aircraft defense systems toward Lebanon’s Bakaa Valley, presumably for delivery to Hizballah, the militant Shi’ite group closely allied with the Assad regime. If they had been deployed, those SA-17 ground-to-air missiles would intimidated Israeli pilots who now operate over Lebanese airspace with impunity, forcing them to higher altitudes and other operational precautions.

A Western intelligence official indicated to TIME that at least one to two additional targets were hit the same night, without offering details. Officials also said that Israel had a “green light” from Washington to launch yet more such strikes.

Hizballah is not Israel’s only concern – or perhaps even the most worrying. Details of the Israeli strikes make clear the risk posed by fundamentalist militants sprinkled among the variegated rebel forces fighting to depose Assad. The jihadists are overwhelmingly home-grown Sunni militants but also include foreigners drawn to the fight from across the Muslim world. Loosely organized into several fighting groups, some fighters embrace the almost nihilist ideology associated with al-Qaeda. But jihadist groups are less vulnerable to the same levers that have proved effective against Syria and other states — such as threats to its territory — or even the frank interests of an organization like Hizballah, which as a political party plays a major role in Lebanon’s government.

“If we succeeded all these years to deter the Syrians and all the other surrounding countries that possess weapons of mass destruction [from making] use of it, it’s because we knew how to deliver the message, that the price would be very high,” Amnon Sofrin, a retired brigadier and former senior Mossad official, told reporters this week. “What kind of threat can you put in the face of a terror organization?”

In other words, it may be easier to attack the problem from the other side — simply destroy the weapons you’re afraid they’ll get their hands on. Among the buildings leveled at the military complex at Jamarya, outside Damascus, were warehouses stocked with equipment necessary for the deployment of chemical and biological weapons, relatively complicated systems typically manned by specially trained forces. The lab facilities dedicated to biological warfare were of special concern, given both the damage that can be done by even small amounts of biological agents, and the interest expressed in such weapons by Osama bin Laden’s successor, Ayman al-Zawahiri. No specific armed force was identified as threatening the compound. Intelligence officials said the concern was unconventional weapons “dripping” into control of extremists in the relative chaos of the rebel side.
One Western intelligence official told TIME the U.S. military was poised to carry out similar airstrikes around Aleppo if rebels threaten to take sites associated with weapons of mass destruction in that region.

Sofrin called that logical. “The world should be worried about the possibility that organizations would possess chemical weapons, because we are not the only target in the Middle East,” he told foreign reporters in Jerusalem on Wednesday. “Let’s go back to 1983, the attack in Beirut on the barracks of the U.S. marines. 241 people killed on Lebanese soil, because they were Americans, strangers.”

Though no country has intervened in Syria’s civil war directly, Western governments were tracking the country’s WMD arsenal even before peaceful street protests were transformed by the brutality of Assad’s response into an armed rebellion that has killed an estimated 60,000 people. But Israel and Washington have worked especially closely from the start, and more visibly in recent weeks.When Israeli warplanes began their attack late Wednesday, Israel’s military intelligence chief, Maj. Gen. Aviv Kochavi was at the Pentagon on a working visit.

Tensions were already rising. The week began with word that Israel had moved two of its Iron Dome missile defense batteries to protect cities in northern Israel, facing the Lebanese border. Prime Minister Benjamin Netanyahu sounded a note of urgency at the weekly meeting of cabinet, the membership of which will be reshaped by a new governing—and yet unformed–coalition following Jan. 22 elections:. “The weapons in Syria are not awaiting the the formation of our government,” Netanyahu said.

After the airstrikes, however, Israeli newspapers brimmed with stories assuring residents that the chances of the attacks being answered militarily were considered low. Assad and Hizballah and Iran, which is closely allied with both, are regarded as too busy trying to save the Syrian regime to open a new front. Israel’s military has been quietly reinforcing its northern front for the last two years. That may be why Syria’s preliminary reaction was a complaint to the United Nations. In diplomatic terms, surgical strikes launched in the name of preventing proliferation of weapons of mass destruction tend to be well-tolerated by the international community, especially when the attacks are not publicly acknowledged. Israel still does not officially acknowledge its secret 2007 destruction of a Syrian nuclear reactor.

“I’m not going to give any condemnation of Israel or rush into any criticism,” British foreign secretary William Hauge told the BBC on Thursday. “There may be many things about it that we don’t know, or the Arab League or Russia don’t know.”

At the same time, Israeli officials raised their guard at embassies and other potential targets overseas, citing Hizballah’s history of seeking retribution through terror attacks. Friday’s suicide bombing at the U.S. embassy in Ankara, Turkey, was attributed to a Turkish leftist group, but made headlines on Hebrew language with a speed driven in part by a new apprehension.